Combined process for hydrocracking of hydrocarbons



9, 1966 JEAN-CLAUDE LAVERGNE ET AL 3,265,610

COMBINED PROCESS FOR HYDROCRACKING OF HYDROCARBONS Filed Dec. 18, 1963 21K 2s 24 25 2'3 29 so :12 2 34 INVENTOR$ vJEAN-CLAUDE LAVERG/VE CLAUDE CLEMENT ROBEPT DUTRIAU ATTORNEY-5 United States Patent 3,265,610 COMBINED PROCESS FOR HYDROCRACKING OF HYDROCARBONS Jean-Claude Lavergne, Le Chesnay, Claude Clement, Bagneux, and Robert Dutriau, Rueil-Malmaison, France, assignors to Institut Francais du Petrole des Carburants et Lubrifiants, Rueil-Malmaison, France Filed Dec. 18, 1963, Ser. No. 331,508 3 Claims. (Cl. 208-30) This invention relates to the hydrocracking of hydrocarbons, and more particularly to a method for the hydrocracking of parafiin hydrocarbons whereby increased yields of paraffin hydrocarbons containing 3 to 4 carbon atoms are obtained.

The increasing demand for paraflin hydrocarbons com posed primarily of molecules containing 3 to 4 carbon atoms has resulted in efforts to produce these desired type of parafiin hydrocarbons by the hydrocracking of heavier hydrocarbons, as for example, those generally classified as gasolines. However, the previously known hydrocracking processes have not given satisfactory results, since catalysts used for this purpose consisting of metals or metal compounds deposited on silica-alumina are not sufficiently active because of the high degree of stability of the C and C parafiins, resulting in low yields of the desired products, while catalysts using 'a support of the molecular sieve type bring about excessive conversion of the heavy hydrocarbons to paraflin hydrocarbons of the C to C type.

The process of the present invention overcomes the disadvantages of the previously known processes in that it provides an effective method of converting mixtures of heavier parafiin hydrocarbons containing at least 20% by weight of paraffin hydrocarbons distilling between 75 and 150 C. under atmospheric pressure and at least 20% of paralfin hydrocarbons distilling between 5 and 75 C. under atmospheric pressure with high yields into paraffin hydrocarbons of the C to C, type. A preferred mixture of hydrocarbons meeting these requirements contains at least 80% by weight of constituents normally distilling between 5 and 150 C. and having a final distillation point below about 220 C. under atmospheric pressure.

According to our improved process for obtaining high yield of paraflin hydrocarbons of the C to C, type, the hydrocarbons of the type described above to be subjected to hydrocracking are first fractionated, preferably by distillation, into a light fraction at least 75% of which dist-ills between 5 and 75 C. and a heavy fraction at least 75 of the constituents of which distill above 75 C.

In our improved process, each of the above fractions is then subjected to separate and distinct operations, and the resulting products of the operations combined, if desired.

The heavy fraction described above is treated with hydrogen under hydrocracking conditions in the presence of a catalyst containing at least one metal or compound of a metal selected from Group VIA and/ or Group VIII of the Periodic Table and at least one acid-cracking agent, such as, for example, silica-alumina, silica-magnesia, silica-magnesia boron oxide, etc. In the case of silicaalumina, the ratio by weight of the silica to alumina selected should be preferably higher than 1 and preferably in the range of 4 to 10. The metallic compound used is preferably nickel, in the metallic state, or nickel oxide, or preferably nickel sulfide if it is preferred to use a compound, the metal selected being present in an amount ranging from 0.5 to 20% be weight of the catalyst. Other metallic compounds suitable for use include, for example, the sulfides and oxides of molybdenum, tungsten and/or cobalt, or mixtures such as, for example, mixtures of 3,265,,6 l0 Patented August 9, 1966 molybdenum oxide with nickel and/or cobalt oxides. These catalysts are well known in the art and hence require no more detailed description.

The hydrocracking treatment of the heavy fraction is effected at a temperature ranging from 300 to 500 C., and preferably between 350 and 440 C. and at a pressure ranging from 30 to 1 20 atmospheres, and space velocity (volume of liquid hydrocarbons/volume of catalyst/hour) of 0.2 to 6.0 and preferably from 0.5 to 2.0, and a hydrogen flow of at least 200 liters, e.g. 400 to 4,000 liters, per liter of liquid hydrocarbon treated.

The reaction product from the hydrocracking operation is fractionated so as to separate the hydrogen and the approximately C to C hyrocarbons, as well as a fraction called light intermediate fraction having the same general characteristics as the above described light fraction (having at least ofits constituents distilling between 5 and 75 C. under atmospheric pressure), which is added to the latter, and another fraction called hydrocracked heavy fraction having the same characteristics as the above-described heavy fraction (having at least 75% of its constituents distilling above 75 C. under atmospheric pressure), this fraction being preferably recycled, although it can also be used as feed-stock in a reforming unit. The C to C fraction likewise can be fractionated in order to separate therefrom the C -C hydrocarbons.

The light fraction of the feed, mixed with the light intermediate fraction, is treated with hydrogen in the presence of a catalyst comprising at least one metal or metallic compound of Group VIA and/ or Group VIII of the Periodic Table, preferably nickel, deposited on a carrier composed of a partially dehydrated metal aluminosilicate known as molecular sieve, the pores of which have a diameter of at least 6 A., eg. between 7 and 13 A.

Other metals or metal compounds which can be incorporated into a support of the type of the molecular sieve include the sulfides or oxides of nickel, cobalt, molybdenum and/or tungsten, or mixtures thereof, [for example, mixtures of molybdenum oxide with cobalt and/ or nickel oxide, but it is to be understood that these cited metals and oxides of metals are only examples for purposes of illustration and that other metals and metal oxides and combinations thereof, as above specified, can also be satisfactorily used.

The metal or metal oxide used in the catalyst advantageously represents from 0.5 to 20% by weight of the catalyst.

The operating conditions are selected within the same range as those previously disclosed as used in the hydrocracking of the heavy fraction of hydrocarbons.

The reaction product from the hydrocracking of the light fraction is fractionated so as to separate principally the hydrogen, the C -C hydrocarbons and the C C hydrocarbons, and the heavier hydrocarbons which are preferably recycled to the light fraction hydrocracking zone.

The present invention will be described below in more detail, with reference to the annexed flow-sheet.

The input charge is introduced into the fractionating column 2 through the conduit 1. To the heavy fraction, withdrawn from the pipe 3, is added hydrogen, conveyed through pipe 4. The resulting mixture passes through the furnace 5 and then into the first hydrocracking zone 6. The effiuent from the latter is then sent by conduit 7 to a first separator 8 where the hydrogen is eliminated and recycled through conduit 9. Fresh hydrogen can be admitted to the system as needed through conduit 10. The liquid phase passes through conduit 11 into a second separator 12 where the hydrocarbons such as methane and ethane are removed, and evacuated through conduit 13. The eflluent then passes into column 14, through conduit 15. At the top of the column essentially the propane and the butanes are separated through pipe 16. The C C hydrocarbons are conveyed through pipe 17 to the furnace 18, after addition thereto of the tailings from the column 1 9, withdrawn through pipe .20, the light fraction from column 2, withdrawn through conduit 21, and the required hydrogen, admitted through conduit 22. The bottom from column 14 is recycled through line 35.

Upon leaving the furnace 18, the hydrogen-hydrocarbon mixture passes by conduit 23 into a second hydrocracking zone 24, then by pipe 25 into the hydrogen separator 26, from which the hydrogen is recycled by pipe 27, and additional fresh hydrogen through pipe 28.

The effiuent passes by pipe 29 into the separator 30 where the methane and ethane are evacuated by the conduit 31. The liquid efliuent passes by the pipe 32 into the column 19 from which the propane and the butanes are withdrawn by pipe 33, while the distillation bottoms from the column is recycled by conduit 20. There is also provided a conduit 34 for the optional withdrawal of the bottom-s from column 19.

The following examples, in which the amounts are indicated in parts by weight, are for the purpose of illustrating our new invention and are not to be taken as limiting in any way, as various change-s therein will be obvious to one skilled in the art and it is specifically understood that we are not limited to the specific amounts of materials, operating procedures or catalyst compositions except as shown by the appended claims.

Example I A continuous current of 100 parts/hour of a Hassi- Messaoud distillate was fractionated into two fractions having the following characteristics:

Light fraction distilling between 35 and 75 C., under atmospheric pressure, at the rate of 30 parts by weight per hour, and containing 74.5% paraflins, 23% naphthenes and 2.5% of aromatics (mean molecular weight: 80).

Heavy fraction distilling between 75 and 142 C. under atmospheric pressure, at the rate of 70 parts by weight per hour, containing 63.9% parafiins, 29.2% naphthenes, and 6.9% of aromatics (mean molecular Weight: 110).

The heavy distillate was mixed with hydrogen at the rate of about 6 moles of hydrogen per mole of hydrocarbons and the mixture passed into a first hydrocracking zone over a catalyst composed of 3% of nickel deposited by impregnation on silica-alumina (87 parts of silica to 13 parts of alumina) and subjected to a sulfurizat-ion treatment by H S, at a temperature of 400 C. under a pressure of 95 kg./cm. and a space velocity (expressed in proportion to the liquid hydrocarbons) of 1 liter/ liter of catalyst/hour. The effiuent was fractionated by distillation into C -C C C and C -C hydrocarbons distilling under atmospheric pressure between 25 and 75 C., and hydrocarbons distilling under atmospheric pressure above 75 C. respectively. The C fraction was recycled, While the C C fraction was mixed with the previously described light distillate. The resulting mixture was then conveyed with about 5 moles of hydrogen per mole of hydrocarbons into a second hydrocracking zone over a catalyst composed of 3% of metallic nickel deposited by impregnation upon a molecular sieve 13X the diameter of the pores of which were of the order of 11 to 12 A. and wherein the atomic ratio Si/Al=1.2. In this second hydrocracking zone the temperature was 420 C., the pressure 70 kg./cm. and the space velocity 1 liter/liter of catalyst/hour. The hydrogen supply corresponded to 5 moles per mole of hydrocarbon (mean meloculer weight: 80).

Upon fractionation of the efliuent there was obtained:

C -C parafiins C C paraflins C hydrocarbons distilling above 25 C. under atmospheric pressure. These latter were recycled into the second hydrocracking zone.

When stable operating conditions were attained there was recovered by distillation an effluent of the following composition from the first hydrocracking zone:

0.4 part/hour of C C paraffins 47.65 parts/hour of C -C paratfins, and

24.1 parts/ hour of C C hydrocarbons which were passed into the second hydrocracking zone, mixed with light distillate of the initial charge boiling at 35 75 C.

From the effluent of this second hydrocracking zone was separated:

11.6 parts/hour of C -C parafiins and 44.2 parts/ hour of C -C paraifins.

Example 11 Example I was repeated except that the catalyst in the first hydrocracking zone was not subjected to the preliminary desulfurization treatment, using an operating temperature of 350 C. and a space velocity of 0.5 liter/liter of catalyst/hour in the first hydrocracking zone.

The reaction conditions in the second hydrocracking zone remained unchanged.

The results obtained were not significantly difierent from those obtained in Example I.

Example III Example I was repeated except that the temperature in the second hydrocracking zone was lowered to 400 C. and the space velocity was 0.8 liter/liter of catalyst/hour.

The results obtained were not significantly difierent from those of Example I.

From the foregoing description, one skilled in the art can readily determine variations to fit particular needs without departing from the basic concept of our invention. All such changes and variations, therefore, are regarded by us as equivalents under the following claims.

What is claimed is:

1. A process for hydrocracking a hydrocarbon feed stock, boiling in a range comprised between 5 and C. under atmospheric pressure, containing at least 20% by weight of paraflinic hydrocarbons distilling in the range of 5 to 75 C. under atmospheric pressure, and at least 20% by weight of parafiinic hydrocarbons distiling in the range of from 75 to 150 C. under atmospheric pressure comprising the stps of:

(a) firactionating said feed stock to a light starting fraction containing at least 75% by weight of constituents distilling between 5 and 75 C. under atmospheric pressure, and a heavy starting fraction containing at least 75% by weight of constituents distilling above 75 C. under atmospheric pressure;

(b) contacting said heavy starting fraction with hydrogen under hydrocracking conditions with a catalyst comprising at least one member of the group consisting of metals and compounds of metals of Groups VIA and VIII of the Periodic Table, and silica-alumina;

(c) fractionating the product of step (b) to a light fraction distilling in the range of C to C hydrocarbons, an intermediate fraction having at least 75 by weight of its constituents distilling between 5 and 75 C. and a heavy hydrocracked fraction distilling above 75 C. under atmospheric pressure;

((1) admixing said intermediate fraction of step (c) with said light starting fraction of step (a);

(e) contacting the mixture of step (d) with hydrogen, under hydrocracking conditions in the presence of a catalyst comprising at least one member of the group consisting of metals and compounds of metals belonging to Group VIA and VIII of the Periodic Table, and at least a partially dehydrated metal alumino-silicate whose pores have a diameter of at least 6 A.; and

( f) fractionating the product of step (e) to a fraction distilling in the range of C to C hydrocarbons and a fraction distilling above C hydrocarbons.

2. A process according to claim 1 wherein the heavy hydrocr-acked hydrocarbon fraction is recycled to the hydrocracking zone for the heavy starting fraction.

3. A process according to claim 1 wherein the fraction containing hydrocarbons having more than 4 carbon atoms in their molecules is recycled to the hydrocracking zone for the light starting fraction.

References Cited by the Examiner UNITED STATES PATENTS Ciapett-a et al 20859 Eng 20826 Myers 20859 Scott et al. 208110 Young 208111 DE-LBERT E. GANTZ, Primary Examiner. 10 A. RIMENS, Assistant Examiner. 

1. A PROCESS FOR HYDROCARCKING A HYDROCARBON FEED STOCK, BOILING IN A RANGE COMPRISED BETWEEN 5* AND 150* C. UNDER ATMOSPHERIC PRESSURE, CONTAINING AT LEAST 20% BY WEIGHT OF PARAFFINIC HYDROCARBONS DISTILLING IN THE RANGE OF 5* TO 75*C. UNDER ATMOSPHERIC PRESSURE, AND AT LEAST 20% BY WEIGHT OF PARAFFINIC HYDROCARBONS DISTILING IN THE RANGE OF FROM 75* TO 150*C. UNDER ATMOSPHERIC PRESSURE COMPRISING THE STEPS OF: (A) FRACTIONATING SAID FEED STOCK TO A LIGHT STARTING FRACTION CONTAINING AT LEAST 75% BY WEIGHT OF CONSTITUENTS DISTILLING BETWEEN 5* AND 75*C. UNDER ATMOSPHERIC PRESSURE, AND A HEAVY STARTING FRACTION CONTAINING AT LEAST 75% BY WEIGHT OF CONSTITUENTS DISTILLING ABOVE 75*C. UNDER ATMOSPHERIC PRESSURE; (B) CONTACTING SAID HEAVY STARTING FRACTION WITH HYDROGEN UNDER HYDROCRACKING CONDITIONS WITH A CATALYST COMPRISING AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF METALS AND COMPOUNDS OF METALS OF GROUPS VIA AND VII OF THE PERIODIC TABLE, AND SILICA-ALUMINA; (C) FRACTIONATING THE PRODUCT OF STEP (B) TO A LIGHT FRACTION DISTILLING IN THE RANGE OF C3 TO C4 HYDDROCARBONS, AN INTERMEDIATE FRACTION HAVING AT LEAST 75% BY WEIGHT OF ITS CONSISTUENTS DISTILLING BETWEEN 5* AND 75*C. AND A HEAVY HYDROCRACKED FRACTION DISTILLING ABOVE 75*C. UNDER ATOMSPHERIC FRACTION (D) ADMIXING SAID INTERMEDIATE FRACTION OF STEP (C) WITH SAID LIGHT STARTING FRACTION OF STEP (A); (E) CONTACTING THE MIXTURE OF STEP (D) WITH HYDROGEN, UNDER HYDROCRACKING CONDITIONS IN THE PRESENCE OF A CATALYST COMPRISING AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF METALS AND COMPOUNDS OF METALS BELONGING TO GROUP VIA AND VIII OF THE PERIODIC TABLE, AND AT LEAST A PARTIALLY DEHYDRATED METAL ALUMINO-SILICATE WHOSE PORES HAVE A DIAMETER OF AT LEAST 6 A.; AND (F) FACTINATING THE PRODUCT OF STEP (E) TO A FRACTION DISTILLING IN THE RANGE OF C3 TO C4 HYDROCARBONS AND A FRACTION DISTILLING ABOVE C4 HYDROCARBONS. 